In a related art, a first radio apparatus is in a sleep mode (i.e., it is not operating except that it performs carrier sensing every constant interval), and a second radio apparatus activates the first radio apparatus by sending it a search request packet that is longer than the above constant interval. If the first radio apparatus is not activated even after the sending of the search request packet, the second radio apparatus sends an even longer packet. In this manner, the operation of the first radio apparatus can be suspended for longer intervals, whereby a low power consumption is realized.